The present invention is generally directed to toner processes, and more specifically, to chemical processes which involve the aggregation and fusion of latex, colorant like pigment, or dye, and additive particles into toner particles, and wherein aggregation can be primarily controlled by utilizing a coagulant of polyaluminum sulfosilicate (PASS), which silicate is commercially available, and is believed to be disclosed in U.S. Pat. Nos. 4,981,675; 5,069,893; 5,149,400; 5,296,213, the disclosures of which are totally incorporated herein by reference; optionally an ionic surfactant as a co-coagulant, such as SANIZOL B.TM., that is a benzylalkonium chloride, and wherein there is preferably selected a latex comprised of, for example, submicron resin particles preferably in the size range of about 0.1 to about 0.4 micron in volume average diameter, suspended in an aqueous phase of water, nonionic and anionic surfactants and optionally suspended in an anionic surfactant to which is added a colorant dispersion comprising, for example, preferably submicron colorant particles in the size range of about 0.08 to about 0.3 micron in volume average diameter, anionic surfactant, or optionally a nonionic surfactant, or mixtures thereof, and wherein the resultant blend is preferably stirred and heated to a temperature below the resin Tg, resulting in aggregates to which optionally is added a second latex, followed by adjusting the pH of the mixture with a base, and heating the mixture to a temperature above the resin Tg to fuse the aggregates.
More specifically, the present invention is generally directed to the aggregation and coalescence or fusion of latex, colorant like pigment, dye, or mixtures thereof, in the presence of polyaluminum sulfosilicate, known initiators, and chain transfer agents, and wherein there are generated toner compositions with, for example, a volume average diameter of from about 1 micron to about 25 microns, and preferably from about 2 microns to about 12 microns, and a narrow particle size distribution of, for example, from about 1.10 to about 1.33, and preferably a size distribution in the range of 1.11 to 1.28, the size and size distribution being measured by a Coulter Counter, without the need to resort to conventional pulverization and classification methods. Furthermore, the present invention in embodiments enables minimum washing, for example about 2 to about 4 washings to provide a suitable toner triboelectrical charge such as greater than about 20 .mu.C/g at 20 percent RH. The toners generated can be selected for known electrophotographic imaging and printing processes, including digital color processes.
Toner generated by the processes of the present invention wherein the coagulant used is polyaluminum sulfosilicate possess a number of advantages as compared to some known emulsion/aggregation processes, these advantages including, for example, a coalescence time of about 0.5 to about 4 hours at a temperature in the range of about 80 to about 95.degree. C. and preferably in the range of about 82.degree. C. to about 90.degree. C. thereby permitting a process reduction time of about 20 to about 40 percent when compared to the use of the same amounts of polyaluminum chloride (PAC). In the embodiments of the present invention wherein when a co-coagulant, such as SANIZOL B.TM. is used in conjunction with the polyaluminum sulfosilicate (PASS), the process time may be further reduced by about 30 to about 50 percent when compared to polyaluminum sulfosilicate alone. Furthermore, the advantage of using a second coagulant, such as SANIZOL B.TM., in combination with PASS over PAC is better retention of colorant. Additionally, with the invention processes in embodiments toner washing can be reduced by about 60 to about 75 percent and the triboelectric charging values of the toner obtained are substantially constant irrespective of the colorant selected. Furthermore, when the toners generated are roll milled and aged over a period of, for example, about 2 to about 3 hours there results stable and negative toner charging with, for example, no wrong sign positively charged toner.
The toners generated with the processes of the present invention are especially useful for imaging processes, especially xerographic processes, which usually require toner transfer efficiency in excess of greater than about 90 percent, such as those with a compact machine design without a cleaner or those that are designed to provide high quality colored images with excellent image resolution, acceptable signal-to-noise ratio, and image uniformity.